Basis of Presentation and Summary of Significant Accounting Policies - Cash, Cash Equivalents and Short- and Long-term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 443,293	$ 366,985	$ 315,442	$ 181,592
Short-term investments	373,959	257,302
Long-term investments	89,343	0
Total cash, cash equivalents, and short- and long-term investments	$ 906,595	$ 624,287